Many types of devices have been developed over the years for the purpose of converting liquids or aerosols into gas-phase fluids. Many such devices have been developed, for example, to desalinate water so as to remove excess salt and other minerals from water. Saline water, or salt water, generally contains a significant concentration of dissolved salts. Seawater has a salinity of roughly 35,000 ppm, or 35 g/L. Seawater is not portable nor suitable for irrigating crops.
Water may be desalinated in order to be converted to fresh water suitable for human consumption or irrigation. Large-scale desalination typically uses large amounts of energy as well as specialized, expensive infrastructure. As such, it is very costly to use desalinated water instead of fresh water from rivers or groundwater.
Three methods of desalination include vacuum distillation, reverse osmosis and multi-stage flash.
In vacuum distillation, water is boiled at less than atmospheric pressure. Boiling of a liquid occurs when the vapor pressure equals the ambient pressure and vapor pressure increases with temperature. Due to the reduction in temperature, energy is saved.
Reverse osmosis technology involves semi-permeable membranes and pressure to separate salts from water. Less energy may be used than thermal distillation. However, desalination remains energy intensive.